It's been a year since Christopher Dorner went on a killing spree to avenge his firing from the Los Angeles Police Department. Over nine days, he killed two civilians and two law enforcement officers and led authorities on a manhunt that crossed Southern California before he died in a burned-out cabin in Big Bear following a shootout. Communities were nervous, and police feared Dorner might target anyone in a uniform.

All of that makes it understandable that police officers were on edge in the early hours of Feb. 7 last year as they took up positions to guard the home of a potential Dorner target in Torrance. Nerves, however, are not an excuse for carelessness, particularly when the result is a fusillade directed at innocent people, in this case two women delivering morning newspapers.

This week, Chief Charlie Beck and the Police Commission rightly decided that the shooting violated department policy. The officers involved could face anything from retraining to termination.

Beck said he empathized with the officers, who truly believed they were under attack by Dorner. But he determined that they jumped to conclusions and misused lethal force. It was simply luck that Margie Carranza and her mother, Emma Hernandez, were not killed in the barrage of more than 100 bullets. In the heat of the moment, the officers overlooked key details: Yes, Carranza's license plate started with an "8D," as did Dorner's, but her truck was a blue Toyota Tacoma, not the gray Nissan Titan with oversized tires and ski rack that he had been driving.

An officer began firing at the women after hearing the smack of a newspaper hitting a driveway and thinking it was a gunshot — a perception that at best suggests jumpiness and that Beck found unreasonable. Officers kept firing even though there was no movement inside the truck. Another officer in the area joined in because he assumed the bullets whizzing by him were from Dorner, when in fact they were fired by his colleagues. One officer fired at the truck 28 times.

It's hard to imagine what could justify firing 28 times at two unarmed women, or that an officer capable of such bad judgment could be trusted in the future. But punishing the officers or their superiors should not end this inquiry, which should additionally determine whether those involved grossly ignored their training or whether the training itself was lacking. Beck is right to hold officers to the highest standards and to demand accountability when they misuse deadly force. He and the commission need to evaluate possible shortcomings in training or tactical procedures that were exposed by this event.

After police officers used batons and rubber bullets on peaceful protesters in MacArthur Park in 2007, the department launched an internal investigation and developed better crowd-control training and policies. This investigation offers a similar opportunity for introspection and improvement; Beck should not waste it.